Conventional search engines support a variety of different types of queries. These queries include informational queries, navigational queries and transactional queries. An informational query is a query submitted by a user, wherein the user is searching for general information about some entity. An example of an informational query may be “Washington”, where the issuer of the query desires to obtain information about the state of Washington. A navigational query is a query issued by the user when the user wishes to find a particular web site or web page. For example, a user wishing to be provided with a web page corresponding to a bank may issue a query of the name of the bank. A transactional query is a query that reflects the intent of the issuer of the query to perform a particular action like purchasing an automobile, downloading a screensaver, or the like.
Search engines are currently being adapted to additionally support fact lookup queries. A fact lookup query is a query that is issued by a user when the intent of the user is to acquire a certain fact about a particular entity. When a fact lookup query is submitted by a user, it is desirable to present a single correct answer to the user rather than a plurality of web pages that may include the correct answer. Examples of fact lookup queries include “population of the state of Washington,” “date of birth of Babe Ruth,” etc. Answering these fact lookup queries through utilization of a search engine has been widely studied in information retrieval and natural language processing. Currently, the focus on answering fact lookup queries has been on natural language processing.
Utilizing natural language processing to perform searches based on fact lookup queries has proven to be a suboptimal solution for a variety of reasons. For example, issuers of queries oftentimes do not submit queries that conform to natural language processing. For instance, rather than issuing the query “what is the capital of Morocco?” searchers tend to issue queries such as “capital of Morocco.” In this case, since the user has not issued an appropriate natural language query, natural language processing may not provide an optimal result. Additionally, most query answering systems based on natural language processing do not have the ability to distinguish fact lookup queries from other queries, and try to answer every query as a fact lookup query. In web search, however, a relatively small portion of queries are fact lookup queries, while the majority of queries are navigational queries, transactional queries, or informational queries. If a web search engine assumes that each issued query is a fact lookup query, the search engine will often provide irrelevant search results to the user.